CN115995874A

CN115995874A - Controller, system and method for managing charging or discharging of heterogeneous battery pack

Info

Publication number: CN115995874A
Application number: CN202210226291.0A
Authority: CN
Inventors: R·夏尔马; S·辛格; 布兰登·奥哈拉; 古川元子; R·凯斯
Original assignee: China Energy Investment Corp Ltd; National Institute of Clean and Low Carbon Energy
Current assignee: China Energy Investment Corp Ltd; National Institute of Clean and Low Carbon Energy
Priority date: 2021-10-20
Filing date: 2022-03-09
Publication date: 2023-04-21
Also published as: US20230119821A1; WO2023065587A1

Abstract

A controller, a system including such a controller, and a method for controlling or managing the discharge or charge of a plurality of battery packs are provided. The controller includes one or more processors and at least one tangible, non-transitory machine-readable medium encoded with one or more programs configured to perform the steps of: the method further includes determining a voltage distribution parameter for each battery pack based on its maximum voltage, its minimum discharge voltage, and the present voltage, assigning a rank to the plurality of battery packs based on the voltage distribution parameter, and determining a respective discharge or charge power based on the rank and the total power demand of each battery pack. The controller provides signals with instructions to the plurality of battery packs and/or the one or more power converters to discharge from or charge to the plurality of battery packs.

Description

Controller, system and method for managing charging or discharging of heterogeneous battery pack

Cross Reference to Related Applications

The present application claims the benefit of U.S. patent application Ser. No.17/506,137, filed 10/20 of 2021, the contents of which are incorporated herein by reference.

Technical Field

The present disclosure relates generally to systems and methods for controlling or managing a battery pack. More particularly, the disclosed subject matter relates to controllers, systems, and methods for managing battery pack charging or discharging, for example, in energy storage applications.

Background

As concerns over environmental issues such as global warming increase, clean and renewable energy sources become more important. These include solar and wind energy and rechargeable batteries. Renewable energy sources are intermittent in that they cannot always be scheduled (dispatched) when needed to meet the changing needs of energy consumers. Energy storage systems are expected to address such flexibility challenges. The stationary energy storage system may store energy and release the energy in the form of electricity when needed.

Disclosure of Invention

The present disclosure provides a controller for controlling or managing the charging or discharging of heterogeneous (heterogenic) battery packs, a system, such as an electrical energy storage system, comprising such a controller, and a method of using the controller.

According to some embodiments, the controller, the system, and the method utilize a technique of ranking a plurality of battery packs based on a voltage distribution parameter of each battery pack. The ranking order of the plurality of battery packs is used as an order of discharging from or charging to the system.

According to some embodiments, a system includes a plurality of battery packs, one or more power converters, and one or more controllers. Each power converter is coupled with at least one of the plurality of battery packs and is configured to convert Direct Current (DC) from one battery pack to Alternating Current (AC) or vice versa. The controller is coupled to the plurality of battery packs and the one or more power converters. In some embodiments, the system may further include more than one controller, and each controller is coupled to a plurality of battery packs.

A plurality of battery packs are defined and described herein. In some embodiments, the plurality of battery packs is a heterogeneous battery pack, which may be selected from a new battery, a secondary Electric Vehicle (EV) battery, or a combination thereof. The plurality of battery packs are connected in parallel, in series, or in a combination thereof (i.e., a hybrid combination). In some embodiments, the plurality of battery packs are connected in parallel.

The controller includes one or more processors and at least one tangible, non-transitory machine-readable medium encoded with one or more programs configured to perform steps for controlling or managing a discharging process or a charging process of a system having a plurality of battery packs. In some embodiments, the steps include: the total power demand (D) (or total scheduled power) required to be scheduled from or charged to the system is received, and characteristic data of each battery pack is collected. The characteristic data of each battery pack includes a maximum voltage (V _{i max} ) Minimum discharge voltage (V) _{i min} ) And the current voltage (V _i ). The characteristic data may also include a maximum total rated power (d _{i max} ) State of health (SOH) and/or state of charge (SOC).

The steps also include V-based _{i max} 、V _{i min} And V _i To determine the voltage distribution parameter (V _i * ). The steps further include the step of determining the voltage distribution parameter (V _i * ) Assigning a ranking to each battery pack as a sequence of discharging or charging to rank the plurality of battery packs, and based on each electricalThe ranking of the battery packs and the total power demand (D) determine a respective discharge or charge power for each battery pack.

The steps further comprise: signals with instructions are provided to the plurality of battery packs and the one or more power converters to discharge from or charge to the plurality of battery packs based on the respective discharge power of each battery pack and/or to keep a particular battery pack idle.

In some embodiments, the controller is configured to determine the voltage distribution parameter (V _i * ) Ranking the plurality of battery packs in ascending, descending, or random order. The power is determined by voltage distribution parameters (V _i * ) Is discharged or charged in ascending, descending or random order. The controller is configured to determine the respective discharge or charge power of each battery by: based on the respective maximum total rated power (d _{i max} ) The respective discharging or charging powers are assigned in the order for discharging or charging until a total power demand (D) is reached. After the total power demand is met, other battery packs with lower ranks may not be assigned to discharge or charge, and the respective discharge or charge power is zero. When the corresponding discharge or charge power of a certain battery pack is zero, that particular battery pack remains idle without discharging or charging.

In some embodiments, the controller is configured to provide a signal with instructions for a predetermined time interval and by repeating the above steps, the respective discharge or charge power of each battery pack is re-determined after the end of the time interval or when a voltage collapse of the battery pack occurs. The controller may be configured to dynamically control the discharging or charging of the plurality of battery packs by temporally updating the respective discharging or charging power of each battery pack over time.

The system may optionally further include one or more Battery Power Management Units (BPMUs). Each BPMU may be connected with one or more battery packs and configured to monitor the one or more battery packs and provide characteristic data of the one or more battery packs to the controller.

In some embodiments, the system is an electrical energy storage system. The total power demand is provided by an upper Energy Management System (EMS). In some embodiments, the controller is configured to discharge power from the plurality of battery packs to the grid or the load, or to charge power from the grid or the load to the plurality of battery packs. In some embodiments, the grid is optional. The power may be discharged to other components requiring power.

In another aspect, the present disclosure provides a controller as described herein for controlling or managing the discharging or charging of a system comprising a plurality of battery packs. As described herein, such a controller includes one or more processors and at least one tangible, non-transitory machine-readable medium encoded with one or more programs configured to perform the steps described herein.

The controller is configured to provide signals with instructions to the plurality of battery packs and the one or more power converters to discharge from (or charge) the plurality of battery packs and/or to keep a particular battery pack idle based on a respective discharge power of each battery pack.

The plurality of battery packs to which the controller is configured to be coupled are heterogeneous battery packs selected from a new battery, a secondary Electric Vehicle (EV) battery, or a combination thereof. The plurality of battery packs are connected in parallel, in series, or in a combination thereof. The controller is configured to control the voltage distribution parameter (V _i * ) Ranking the plurality of battery packs in ascending, descending, or random order. The power is determined by voltage distribution parameters (V _i * ) Is discharged or charged in ascending, descending or random order.

The controller is configured to provide instructions to the signals for a predetermined time interval and by repeating the steps, the respective discharge or charge power of each battery pack is re-determined after the end of the time interval or when a voltage collapse of the battery pack occurs. The controller is further configured to dynamically control the discharging or charging of the plurality of battery packs by temporally updating the respective discharging or charging power of each battery pack over time.

The controller is configured to control, for example, discharging or charging of a heterogeneous battery in an electrical energy storage system. In some embodiments, the controller is configured to discharge power from the plurality of battery packs to a grid or load, or to charge power from the grid or load to the plurality of battery packs.

In another aspect, the present disclosure provides a method for controlling or managing discharge or charge of a system comprising a plurality of battery packs by a controller within the system as described herein. The method comprises the following steps: the total power demand D required to be scheduled from or charged to the system is received, and characteristic data of each battery pack is collected. The characteristic data of each battery pack includes a maximum voltage (V _{i max} ) Minimum discharge voltage (V) _{i min} ) And the current voltage (V _i ). Other data may include SOH, SOC, and maximum total rated power (d) for each battery pack _{i max} )。

The method further comprises the steps of: based on V _{i max} 、V _{i min} And V _i Determining a voltage distribution parameter (V _i * ) By the voltage distribution parameter (V _i * ) Each battery pack is assigned a ranking that is a discharge or charge order to rank the plurality of battery packs, and a respective discharge or charge power for each battery pack is determined based on the ranking of each battery pack and the total power demand (D).

In such a method, the controller also provides signals with instructions to the plurality of battery packs and the one or more power converters to discharge or charge the plurality of battery packs based on the respective discharge or charge power of each battery pack and/or to keep a particular battery pack idle as described herein. In some embodiments, instructions are sent from the controller to each battery pack and/or one or more converters connected to the plurality of battery packs for discharging or charging based on the respective discharging or charging power of each battery pack.

The plurality of battery packs are heterogeneous battery packs selected from a new battery, a secondary Electric Vehicle (EV) battery, or a combination thereof. The plurality of battery packs are connected in parallel, in series, or in a combination thereof.

According to some embodiments, equation (1) is used to determine the voltage distribution parameter (V _i *)：

V _i *＝(V _i -V _{i min} )/(V _{i max} -V _{i min} ) (1)

In some embodiments, the plurality of battery packs are configured to provide a voltage distribution parameter (V _i * ) Is ranked in increasing order. In some other embodiments, the plurality of battery packs are configured to provide a voltage distribution parameter (V _i * ) Is ranked in descending order. Alternatively, the plurality of battery packs are arranged in accordance with a voltage distribution parameter (V _i * ) Is ranked in a random order. In each case, the respective discharge or charge power of each battery is determined by: based on the respective maximum total rated power (d _{i max} ) The respective discharge or charge powers are assigned in a discharge or charge order until a total power demand (D) is reached. The corresponding discharge or charge power of the other battery packs is zero. When the corresponding discharge or charge power is assigned to zero, a certain battery pack remains idle.

In some embodiments, some or all of the above steps are repeated to re-determine the respective discharge or charge power of each battery pack after the end of a predetermined time interval or when a voltage collapse of the battery pack occurs. The discharge process of the plurality of battery packs may also be dynamically controlled by instantaneously updating the respective discharge or charge power of each battery pack over time.

The systems, controllers, and methods provided in the present disclosure provide a number of advantages. For example, various new and used battery packs having different qualities may be used. There is no need to pre-select or remove the battery pack. Multiple heterogeneous battery packs commonly supply a power load to meet power demand, while each battery pack may be discharged in different shares. As described herein, the systems, controllers, and methods selectively extend the life of a battery pack having higher or lower V or the life of all battery packs, and they also provide flexibility in maintaining and upgrading the system.

Drawings

The disclosure is best understood from the following detailed description when read in connection with the accompanying drawing figures. It is emphasized that, according to common practice, the various features of the drawing are not necessarily drawn to scale. On the contrary, the dimensions of the various features are arbitrarily expanded or reduced for clarity. Like reference numerals refer to like features throughout the specification and drawings.

Fig. 1 is a block diagram illustrating an exemplary system including a heterogeneous battery pack and a controller, according to some embodiments.

Fig. 2 is a block diagram illustrating an exemplary controller for controlling or managing charging or discharging of a plurality of heterogeneous battery packs, the exemplary controller including one or more processors and at least one tangible, non-transitory machine-readable medium encoded with one or more programs, according to some embodiments.

Fig. 3 illustrates a relationship between voltage (V) and charge flow (Ah) of an exemplary battery pack in some embodiments.

Fig. 4 is a flowchart illustrating an exemplary method for controlling discharge of a plurality of battery packs according to some embodiments.

Fig. 5 shows the total power demand or schedule required from an exemplary system comprising four battery packs (battery packs 1, 2, 3 and 4) at different time intervals (each having 15 minutes) when each battery pack is equally ranked and thus equally discharged.

Fig. 6-9 show the respective discharge power from each battery pack (battery packs 1, 2, 3 and 4, respectively) to meet the total power demand as shown in fig. 5.

Fig. 10 shows the total power demand or schedule required from an exemplary system comprising four battery packs (battery packs 1, 2, 3 and 4) at different time intervals (15 minutes), wherein the battery packs are ranked as a discharge order in order of increasing voltage distribution parameter (V x) and the battery pack with the lowest V x is discharged first.

Fig. 11-14 show the respective discharge power from each battery pack (battery packs 1, 2, 3 and 4, respectively) to meet the total power demand as shown in fig. 10.

Detailed Description

The description of the exemplary embodiments is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description. In the description, relative terms such as "lower," "upper," "horizontal," "vertical," "above," "below," "upward," "downward," "top" and "bottom" as well as derivatives thereof (e.g., "horizontally," "downwardly," "upwardly," etc.) should be construed to refer to the orientation as then described or as shown in the drawing under discussion. These relative terms are for convenience of description and do not require that the apparatus be constructed or operated in a particular orientation. Terms concerning attachments, coupling and the like (e.g., connection and interconnection) refer to a relationship wherein structures are secured or attached to one another either directly or indirectly through intervening structures, as well as both movable or rigid attachments or relationships, unless expressly described otherwise.

For the purposes of the following description, it is to be understood that the embodiments described below may take on alternative variations and embodiments. It should also be understood that the specific articles, compositions, and/or methods described herein are exemplary and should not be considered limiting.

In this disclosure, the singular forms "a", "an" and "the" include plural references, and reference to a particular value includes at least that particular value unless the context clearly indicates otherwise. When values are expressed as approximations, by use of the antecedent "about," it will be understood that the particular value forms another embodiment. As used herein, "about X" (where X is a numerical value) preferably means ± 10% of the referenced value, inclusive. For example, the phrase "about 8" preferably refers to a value of 7.2 to 8.8, inclusive. When present, all ranges are inclusive and combinable. For example, when a range of "1 to 5" is recited, the recited range should be interpreted to include the ranges "1 to 4", "1 to 3", "1-2 and 4-5", "1-3 and 5", "2-5", and the like. In addition, when a list of alternatives is provided positively, such list may be interpreted to mean that any alternatives may be excluded, which may be done, for example, by a negative limitation in the claims. For example, when a range of "1 to 5" is recited, the recited range can be interpreted to include a case in which any one of 1, 2, 3, 4, or 5 is negatively excluded; thus, a recitation of "1 to 5" may be interpreted as "1 and 3-5, but not 2", or simply "wherein 2 is not included". "means that any component, element, property, or step recited herein may be expressly excluded in the claims whether or not such component, element, property, or step is listed as a substitute or whether or not it is individually recited.

As referred to herein, "heterogeneous battery pack" refers to a battery pack or module having different capacities, states of charge (SOCs), states of health (SOHs), and/or voltages, and may be selected from new batteries (e.g., from different manufacturers), secondary use Electric Vehicle (EV) batteries, or combinations thereof. The secondary use EV battery is for illustration purposes. References to "discharging" or "charging" of multiple battery packs are understood to mean that the multiple battery packs are commonly discharged or charged while some battery packs may remain idle (without charging or discharging).

Reference herein to "state of health (SOH)" will be understood to refer to the quality factor of a battery, cell or stack of batteries as compared to its ideal condition, unless explicitly stated otherwise. SOH is characterized in percent (%). The condition matching the specification under ideal conditions is 100%. SOH may decrease over time and use.

Unless specifically indicated otherwise, a "state of charge" (SOC) as described herein is defined as the charge level of a battery relative to its capacity. The unit of SOC is a percentage point, 0% representing empty and 100% representing full.

The term "human-machine interface (HMI)" as used herein is understood to refer to a User Interface (UI), which is the space where interaction between a person and a machine occurs. A human-machine interface (HMI) may involve an interface between man-machine with physical input hardware such as a keyboard, mouse, or any other human-machine interaction based on touch, vision, or hearing. Such user interfaces may include other layers such as output hardware, e.g., computer monitors, speakers, and printers.

The term "Energy Management System (EMS)" as used herein refers to a system of computer-aided tools used by an operator of a utility grid to monitor, control and optimize the performance of a power generation or transmission system.

In this disclosure, the terms "power demand", "power schedule" and "power demand" are used interchangeably and may refer to the power required for a discharge or charge process. The terms "converter" and "inverter" may be used interchangeably. Each battery pack includes an inverter and a Battery Management Unit (BMU) therein. For ease of description, the term "power inverter" or "AC/DC power converter" is used to describe the internal components in a battery, and the term "power converter" or "Power Conversion System (PCS)" is used to describe a converter that is connected to one or more battery. The term "Battery Management Unit (BMU)" or "Battery Management System (BMS)" is used to describe internal components in a battery pack, and the term "Battery Power Management Unit (BPMU)" is used to describe a battery management unit connected to one or more battery packs.

In this disclosure, the terms "power" and "energy" are used interchangeably, and energy is described in units of time. The energy and power may be converted over time.

The terms "connected" or "coupled" as used herein are understood to encompass different connections or couplings between the components, to conduct electrical energy or to transmit signals for communication, unless specifically indicated otherwise. Such connection or coupling may be through wired, wireless or cloud-based modes.

Power scheduling (discharging) is a function of charge flow and voltage. The scheduling energy is defined as the scheduling power over a user-specified period of time. For the same amount of charge flow, a higher voltage discharge provides higher power than a lower voltage discharge. Early approaches did not consider the impact of voltage on the decision of power or energy scheduling. In addition, the non-uniformity of the voltage of the battery pack and the voltage trace during discharge has not been considered.

The heterogeneous battery packs may be pre-classified before use. For example, cells or battery packs having similar performance may be grouped to make new battery packs or systems. State of charge (SOC) may be used as a criterion for choosing a battery or a battery pack. However, such classification prior to use is not dynamic. There is a need for a more efficient method of using heterogeneous batteries.

The present disclosure provides a controller for controlling the discharge or charge of a heterogeneous battery, a system, such as an electrical energy storage system, including such a controller, and methods of using the controller. The present disclosure provides such a controller, such a system, and such a method to efficiently utilize heterogeneous batteries in energy storage applications, such as new batteries from different manufacturers or secondary use Electric Vehicle (EV) battery packs. Each battery pack is individually operated according to its characteristics (e.g., voltage distribution parameters). There is no need to pre-select or disassemble the battery pack. According to some embodiments, the controller, the system, and the method utilize a technique of ranking a plurality of battery packs based on a voltage distribution parameter (V) of each battery pack other than SOC. The ranking order of the plurality of battery packs is used as an order of discharging from or charging to the system. The priority of discharging or charging the plurality of battery packs is determined by the voltage distribution parameters as described herein.

The controller, system and method provided in the present disclosure are applicable to different battery packs. The battery may have the same or different chemical properties, the same or different performance or degradation, the same or different physical and/or electrical properties. In some embodiments, the battery pack is a heterogeneous battery pack.

In fig. 1-2, like items are denoted by like reference numerals, and the description of the structure provided above with reference to the previous figures is not repeated for the sake of brevity. The method depicted in fig. 4 is described with reference to the exemplary structures depicted in fig. 1-2 and the data sketch depicted in fig. 3.

Referring to fig. 1, an exemplary system 100 includes one or more power converters 10, a plurality of battery packs 20, and a controller 60. The number and configuration of each component in fig. 1 is for illustration only. The system may have any suitable number of each component in any suitable combination or configuration.

Each power converter 10 is coupled to at least one of the plurality of battery packs 20 and is configured to convert Direct Current (DC) from the battery pack to Alternating Current (AC) or vice versa. The power converter 10 may also be referred to as a Power Conversion System (PCS) or an inverter.

The controller 60 is connected to a plurality of battery packs 20 and one or more power converters 10 in some embodiments, the system may also include more than one controller 60, and each controller 60 is coupled to a plurality of battery packs 20.

The controller 60 may be directly or indirectly coupled to the plurality of battery packs 20. For example, in some embodiments, the exemplary system 100 may optionally further include one or more Battery Power Management Units (BPMUs), which may also be referred to as Battery Management Units (BMUs). Each BPMU 30 may be connected with one or more battery packs 20 and configured to monitor the one or more battery packs 20 and provide characteristic data of the one or more battery packs 20 to the controller 60. In some embodiments, the controller 60 is configured to read data from each battery pack 20. This may be accomplished by each respective BPMU 30 connected with each battery pack.

The plurality of battery packs 20 are heterogeneous battery packs, which may be selected from a new battery, a secondary Electric Vehicle (EV) battery, or a combination thereof. The plurality of battery packs 20 are connected in parallel, in series, or in a combination thereof. In some embodiments, the plurality of battery packs 20 are connected in parallel. The lack of a series connection between the battery packs eliminates circulating current and losses.

As shown in fig. 1, the plurality of battery packs 20 are connected in a parallel configuration 50. In some embodiments, the plurality of battery packs 20 are secondary use (i.e., used) Electric Vehicle (EV) batteries. The EV battery used can be used directly in the system without pre-selection or disassembly. Each battery pack 20 includes one or more batteries. Each battery pack 20 may include an internal Battery Management Unit (BMU) and an internal inverter. EV battery pack 20 is removed from the vehicle and is not disassembled into modules. These EV battery packs 20 can be subjected to simple tests to verify their SOH.

In some embodiments, the exemplary system 100 is an electrical energy storage system. The controller 60 is configured to receive a total power demand provided from an upper Energy Management System (EMS) 110. In some embodiments, the controller 60 is configured to discharge power from the plurality of battery packs 20 for direct current to an ac grid or load 85. The exemplary system 100 may be used to discharge power from the battery pack 20 to the grid 85 or to charge power from the grid 85 to the battery pack 20. Wire connections 12 may be used. An alternative power cable is shown by the dashed line 13 in fig. 1. There may be multiple power cable topologies between the converter 10 and the battery pack 20. The system 100 directly uses the grid-tied AC/DC converter 10 with size expansion flexibility. Grid-tied applications do not require additional power conversion systems.

In some embodiments, the grid 85 is optional. The power may be released to other components that require electrical power.

The controller 60 may be connected to other components in a wired or wireless mode. In the exemplary system 100 shown in fig. 1, the controller 60 may be connected with other components such as the converter 10, the BPMU 30, and the EMS 110 via a data cable or wireless connection 22. The BPMU 30 may also be connected with the battery pack 20 via a data cable or wireless connection 22. The controller 60 may operate in a cloud-based mode.

Each battery pack 20 may be connected to the power converter 10 (or a separate DC port on the converter 10) by a set of automatic DC breakers (not shown) that activate and control the connection between the battery pack 20 and the converter 10. Converter 10 controls whether to charge or discharge a single EV battery pack 20 by following instructions from controller 60.

Referring to fig. 2, the controller 60 includes one or more processors 62 and at least one tangible, non-transitory machine readable medium encoded with one or more programs configured to perform steps for controlling a discharge process of a system having a plurality of battery packs. The controller 60, processor 62 and/or program 74 may be external to the converter 10 or internal to the converter 10.

The processor(s) 62 may include a central controller 64 that includes a parameter input module 66, a model module 68, a parameter control module 70, and an information and instruction module 72. The parameter input module 66 coordinates with the battery pack 20 (optionally the BPMU 30 and HMI or EMS 110) to read data from the battery pack 20 and power requirements from the HMI or EMS 110. The parameter input module 66 is also coordinated with each power converter 10. The parameter control module 70 coordinates with each power converter 10 and each battery pack 20, and optionally with the BPMU 30 and HMI or EMS 110 to control the discharge process. Together with one or more programs 74, the model module 68 is configured to perform simulations based on input parameters to provide information and instructions to the parameter control module 70 and the information and instructions module 72. The processor 62 may optionally be coupled to one or more displays 76 for displaying information and instructions from the module 72 and to an operator.

The controller 60 and the processor 62 with the program 74 are configured to perform a discharging or charging step as described herein. As described in fig. 4-6, in some embodiments, the controller 60 is configured to perform the steps described herein. The steps include: the total power demand D required to be scheduled from the system or charged to the system 100 is received and characteristic data of each battery pack 20 is collected. The total power demand D is the total energy required per unit time. The characteristic data of each battery pack 20 includes at least a maximum voltage (V _{i max} ) And a minimum discharge voltage (V) _{i min} ) Which may be derived from a voltage versus charge curve (e.g., fig. 3) for each battery pack 20. The characteristic data may also include a maximum total rated power (d _{i max} In kilowatts) and the current voltage (V _i ). The characteristic data may also include capacity, state of health (SOH), and/or state of charge (SOC), among other parameters, of each battery pack.

The steps also include V-based _{i max} 、V _{i min} And V _i To determine the voltage distribution parameter (V _i * ). The steps also include by each battery pack 20Voltage distribution parameter (V) _i * ) Each battery pack 20 is assigned a ranking as an order of discharging or charging, the plurality of battery packs 20 are ranked, and a respective discharging or charging power for each battery pack is determined based on the ranking and the total power demand (D) for each battery pack. The number of battery packs is denoted as "n". The subscript "i" denotes a battery pack from 1 to n.

In some embodiments, the controller 60 is configured to determine the voltage distribution parameter (V _i * ) The plurality of battery packs 20 are ranked in ascending, descending, or random order. The ranks are assigned from "1" to "n", where n is the number of total battery packs. Rank "1" as the highest rank has the highest discharge or charge priority. The discharge or charge of the power is controlled by a voltage distribution parameter (V _i * ) In ascending, descending or random order. The controller 60 is configured to determine the respective discharge or charge power of each battery 20 by: based on the respective maximum total rated power (d _{i max} ) The respective discharging or charging powers are assigned in the order of discharging or charging until the total power demand (D) is reached. After the total power demand is met, other battery packs with lower ranks may not be assigned to discharge or charge, and the corresponding discharge or charge power is zero. When the corresponding discharge or charge power of a certain battery pack is zero, that particular battery pack remains idle without discharging or charging. Sometimes the battery pack cannot be used for discharging because its voltage is equal to or lower than its minimum discharge voltage (i.e., has a voltage collapse), the particular battery pack 20 remains idle without discharging. Such a battery pack 20 may need to be charged or replaced first.

In some embodiments, the controller 60 is configured to provide a signal with instructions for a predetermined time interval and by repeating the above steps, the respective discharge or charge power of each battery pack 20 is re-determined after the end of the time interval or when a voltage collapse of the battery pack occurs. The controller 60 may be configured to dynamically control the discharging or charging of the plurality of battery packs 20 by temporally updating the respective discharging or charging power of each battery pack over time.

The present disclosure provides a controller 60 as described herein for controlling the discharge of a system 100 comprising a plurality of battery packs 20. The controller 60 is configured to control, for example, discharging or charging of the heterogeneous battery pack 20 in an electrical energy storage system. The controller 60 is configured to discharge power from the plurality of battery packs 20 to a grid or load 85 or to charge power to the plurality of battery packs 20.

The present disclosure also provides a method 200 for controlling the discharging or charging of a system 100 comprising a plurality of battery packs 20, by a controller 60 in the system as described herein.

Different battery packs, in particular second life or used batteries or batteries with different capacities and ratings, have varying voltage-charging characteristics. The controller 60 and method 200 in the present disclosure bias the discharge of a battery pack having a lower or higher voltage distribution parameter (V).

Referring to fig. 3, an exemplary plot of voltage versus charge flow of an exemplary battery pack 20 during a discharge process is shown. The input parameters may include voltage, current, and time. The charge or charge flow (Q) is calculated from the current and the elapsed time. The voltage is in volts (v) and the charge flow is in ampere-hours (Ah) or coulombs. As shown in fig. 3, vmax is the voltage of such a battery pack when it is fully charged or at its maximum allowable charge level. Vmin is the voltage of such a battery when it runs out of charge or reaches its minimum allowable charge level.

The voltage versus charge curve may be empirically generated at a constant discharge level while monitoring the current during the discharge period until the voltage drop exceeds a user-defined minimum limit (Vmin), as shown by the vertical dashed line in fig. 3. The current and voltage follow the same or similar trend as the charging time increases. In some embodiments, the voltage versus charge curve is empirically generated at a constant discharge level while monitoring the current during the discharge period until the voltage drop exceeds a user-defined minimum limit, as indicated by the intersection of the dashed vertical line with the horizontal line from the y-axis.

Different discharge rates may produce different voltage discharge curves for the same battery pack. A family of curves of different discharge rates may be provided for each respective battery pack 20 and may be used to track the voltage trajectories of the battery packs for a given scheduled event. In some embodiments, a representative curve is obtained using techniques such as extrapolation, interpolation, or averaging. In one curve, such a battery shows a significantly higher voltage gradient and depletes faster when the voltage decreases beyond Vmin during discharge. The lower limit point may also be referred to as a voltage collapse. In some embodiments, vmax and Vmin are open circuit voltages specified by the manufacturer or derived from a predetermined voltage-charge curve. The range from Vmin to Vmax can be in the range from 400 volts to 1,000 volts.

The voltage distribution parameter V of the battery pack 20 having the current voltage (V) is defined as (V-Vmin)/(Vmax-Vmin). The higher the parameter, the higher the extent to which the battery pack can be discharged further. For example, in some embodiments, the exemplary battery packs used have V in the range from 50% to 95%.

Fig. 4 illustrates an exemplary method 200 for controlling or managing the charging or discharging of a plurality of battery packs 20 in the system 100, according to some embodiments. The plurality of battery packs 20 are heterogeneous battery packs selected from a new battery, a secondary Electric Vehicle (EV) battery, or a combination thereof. The plurality of battery packs 20 are connected in parallel, in series, or in a combination thereof. The plurality of battery packs 20 are preferably connected in parallel.

Referring to fig. 4, at step 202, the controller 60 receives the total power demand that needs to be scheduled from or charged to the system 100. As described herein, the total power demand may be received from EMS 110.

At step 204, characteristic data for each battery pack 20 is collected. A voltage versus charge curve for each battery pack 20 may be established. The voltages and charges in the curve may be referred to as a first set or initial value. As described above, an exemplary curve is shown in fig. 3. The voltage versus charge (Amp-hr) characteristics of each battery may be empirically obtained or derived for a set of frequently encountered discharge rates. This provides a family of curves that can be used for tracking the feedThe voltage trace of the battery pack for a scheduled period. The characteristic data of each battery pack includes a maximum voltage (V _{i max} ) Minimum discharge voltage (V) _{i min} ) And the current voltage (V _i ). The data may include a maximum total rated power (d) for each battery pack 20 _{i max} ) SOH, and SOC.

The minimum and maximum voltages of each battery pack may be calculated according to the number of battery cells in each battery pack and the configuration in which the battery cells are arranged. For example, if the maximum and minimum voltages of each cell are 4.2V and 3.5V, respectively, and the battery pack includes 144 cells, the Vmax of the battery pack is 4.2×144V, and the Vmin of such battery pack is 3.5×144V.

In step 206, based on V _{i max} 、V _{i min} V (V) _i To determine the voltage distribution parameters (V) _i * ). In some embodiments, the voltage distribution parameter (V _i * ) To determine V by using equation (1) to determine the voltage distribution parameter (V _i *)：

V _i *＝(V _i -V _{i min} )/(V _{i max} -V _{i min} ) (1)

In step 210, according to the voltage distribution parameters (V _i * ) Each battery pack is assigned a respective ranking as a discharging or charging order, thereby ranking the plurality of battery packs 20.

At step 212, a respective discharge or charge power for each battery pack is determined based on the ranking of each battery pack and the total power demand (D). The priority or sequential ranking of discharging or charging is assigned from 1, 2, 3 to n, n being the number of battery packs 20 in the system. The ranking of "1" which is considered the highest level means that the total power demand (D) is satisfied first using the corresponding battery pack.

In some embodiments, the plurality of battery packs 20 are configured with a voltage distribution parameter (V _i * ) Is a sequential order of increasing order. In addition, the battery group with the smallest V is assigned to "1". In other embodiments, the plurality of battery packs 20 are arranged in accordance withVoltage distribution parameter (V of each battery pack 20 _i * ) Is a descending order of ranking of (2). The highest V group is assigned to "1". Alternatively, the plurality of battery packs 20 are arranged in accordance with the voltage distribution parameter (V _i * ) Is a random order of ranking of (1). In each case, the respective discharge or charge power of each battery is determined by: based on the capacity of each stack (e.g., maximum total rated power (d _{i max} ) And/or state of charge, each battery is assigned its own discharge or charge power in the order of discharge or charge (starting from rank 1) until the total power demand (D) is reached. If the total power demand is met by some but not all of the battery packs, the respective discharge or charge power of the other battery packs may be zero. The certain battery pack remains idle when the corresponding discharge or charge power is assigned to zero.

In some embodiments, the capacity (in kWh) of all battery packs E and the design charge power Pd (in kW) of the system are known. The duration Td (hours) of the system can be calculated by the equation td=e/Pd. Maximum total rated power (d _{i max} kW) may be calculated by dividing the capacity of a single battery pack by the duration. Such calculations may also be performed for discharging or charging.

For illustrative purposes only, three embodiments are described below with respect to

steps

210 and 212.

First embodiment:

the plurality of battery packs 20 are arranged in accordance with the voltage distribution parameter (V _i * ) Is arranged in ascending order. The battery pack having the lowest V is assigned to "1" (i.e., the highest priority for discharging or charging), and the battery pack having the highest V is assigned to "n" (the total number of battery packs). The power demand (D), otherwise known as total scheduled power (Dd), required by the EMS is provided to the system at time intervals of, for example, 15 minute increments. The respective power discharge (ddi) of each battery is determined according to the ranking, starting from ranking "1", ddi =ddimax until Sum (ddi) =dd. The maximum total rated power is denoted "ddimax". The corresponding discharge power (ddi) may be limited by the maximum discharge (or charge) capability and may also be based on the corresponding discharge power (ddi) and the charge-likeState (SOC). If some of the battery packs can be discharged to meet the total power demand (DD), the remaining other battery packs have a corresponding discharge power of zero (i.e., ddi =0).

In the present disclosure, among the parameters "D", "Dd" and "Dc" that may be used interchangeably, the letters "D" and "c" are used to denote "discharge" and "charge", respectively. Similarly, the parameters "ddi" and "dci" may be interchanged with "di". The discharge power may have an absolute value higher than zero in units such as kWh, but the discharge power is represented by a negative value and the charge power is represented by a positive value.

Ranking may be performed if desired when the EMS provides a signal that power is available to charge Dc. The ranking may be the same as described above. The corresponding charging power (dci) may be determined according to: the battery with Vi < Vimax is first selected and then ranked by V, with rank "1" assigned to the battery with the lowest V, as described above. The corresponding power charge (dci), dci=dcimax, is determined from the ranking until Sum (dci) =dc. The battery with the lowest V will be assigned 100% charge first and then move to the next lowest V until Sum (dci) =dc. Other battery packs may be assigned with zero charge (i.e., dci=zero), if desired.

The method in the first embodiment provides advantages in addition to those described herein. For example, a battery with lower V (which is a weaker battery) may be used and depleted first to extend the life of the stronger battery. After repeated use, these weak battery packs may not work and are replaced. A healthier system may be established.

Second embodiment:

the plurality of battery packs 20 are arranged in accordance with the voltage distribution parameter (V _i * ) Is a descending order of ranking of (2). The battery with the highest V is assigned to "1" and the battery with the lowest V is assigned to "n". The power demand (D), otherwise known as total scheduled power (Dd), required by the EMS is provided to the system at time intervals of, for example, 15 minute increments. The respective discharge power (ddi) of each battery pack is determined according to the ranking,starting from rank "1", ddi =ddimax until Sum (ddi) =dd. The maximum total rated power is denoted "ddimax". The respective discharge power (ddi) may be limited by a maximum discharge (or charge) capability and may also be determined based on the respective discharge power (ddi) and/or state of charge (SOC). If some of the battery packs can be discharged to meet the total power demand (Dd), then other battery packs have a corresponding discharge power of zero (i.e., ddi =0).

The ranking process may be performed if desired when the EMS provides a signal that power is available to charge Dc. The ranking may be the same as the ranking prior to the discharge process as described above. The corresponding charging power (dci) may be determined according to: the battery with Vi < Vimax is first selected and then ranked by V, with rank "1" assigned to the battery with highest V, as described above. The respective charging powers (dci) are determined according to the ranking, dci=dcimax until Sum (dci) =dc. The battery with highest V will be assigned 100% charge first and then move to the next highest V until Sum (dci) =dc. Other battery packs may be assigned with zero charge (i.e., dci=zero), if desired.

The method in the second embodiment provides advantages in addition to those described herein. For example, the battery with the highest V (which is the stronger battery) may be used first to extend the life of the weaker battery and the overall system, especially when replacement of the weaker battery may not be available.

Third embodiment:

the plurality of battery packs 20 are arranged in accordance with the voltage distribution parameter (V _i * ) Is a random order of ranking of (1). A random program may be used to randomly select the V values from the data set and to select the corresponding battery packs. Similarly, all battery packs are randomly assigned ranks from "1" to "n". The power demand (D), otherwise known as total scheduled power (Dd), required by the EMS is provided to the system at time intervals of, for example, 15 minute increments. The respective discharge power (ddi) of each battery is determined according to the ranking, starting from ranking "1", ddi =ddimax until Sum (ddi) =dd. The maximum total rated power is denoted "ddimax".The respective discharge power (ddi) may be limited by a maximum discharge (or charge) capability, and may also be determined based on the respective discharge power (ddi) and state of charge (SOC). If some of the battery packs can be discharged to meet the total power demand (Dd), then other battery packs have a corresponding zero discharge power (i.e., ddi =0).

When the EMS provides a signal that power is available to charge Dc, the battery packs may be randomly ranked again. The corresponding charging power (dci) may be determined according to: a battery pack with Vi < Vimax is first selected and then ranked according to V, where a rank of "1" is assigned to the battery pack. The respective charging powers (dci) are determined according to the ranking, dci=dcimax until Sum (dci) =dc. The battery pack with rank 1 will be assigned a 100% charge first and then move to the next rank (e.g., 2,3 to n) until Sum (dci) =dc. Other battery packs may be assigned with zero charge (i.e., dci=zero), if desired.

The method in the third embodiment provides advantages in addition to those described herein. For example, battery packs having different V are used randomly. Randomization in the ranking ensures that the battery packs are used uniformly over a period of time even though a subset of the battery packs are used at a particular time to meet scheduling requirements from the EMS. This approach extends the life of all battery packs and the overall system. This approach is useful when the battery pack in the system is relatively good and uniform.

In summary, the method provided by the present invention utilizes a series of heterogeneous battery packs to provide consistent and persistent scheduling distribution according to a V-based ranking process to meet the scheduling needs of EMS discharge or charge. The managed throughput results in improved life and performance of the energy storage system.

Referring back to fig. 4, at step 214, signals having instructions are provided from controller 60 to the plurality of battery packs 20 and the one or more power converters 10 to discharge from or charge each battery pack 20 based on its respective discharge or charge power. If the corresponding power is zero, the certain battery pack remains idle.

According to the instruction, power from the plurality of battery packs 20 is discharged or power is to be charged to the battery packs 20. After each process, an alternating voltage versus charge curve may be generated for each battery pack and used to generate the voltage distribution parameters at step 206. Sometimes, the curves may be the same.

The discharge energy is assumed to be delivered per unit time. Thus, energy is synonymous with power for scheduling purposes.

Referring to fig. 4, in some embodiments, the method 200 further includes a reassignment (or redetermination) step or loop 220. In step 214, the controller 60 provides a signal with instructions at predetermined time intervals. The interval may be defined by a user. For example, the time interval may be any length of time from 10 seconds to 2 hours, for example, 1 minute, 2 minutes, 5 minutes, 10 minutes, 15 minutes, 30 minutes, or one hour. After step 220, the controller reassigns the discharge or charge power of the plurality of battery packs after the end of the time interval or when a voltage collapse of the battery packs occurs by repeating some or all of the

steps including steps

202, 204, 206, 210, 212 and 214. In some embodiments, the reassignment process returns to and begins at step 202. In some embodiments, the reassignment process returns to and begins at step 204. The discharge process of the plurality of battery packs may also be dynamically controlled by instantaneously updating the respective discharge or charge power of each battery pack over time. The time interval may be very short or minimal.

In some embodiments, the system 100 includes a heterogeneous battery pack 20 integrated with a bi-directional converter (or inverter) 10 connected to a grid or micro-grid 85 that can be remotely or locally scheduled using this intelligent algorithm running in a local or cloud-based controller 60. In some embodiments, the algorithm requires a priori knowledge about the voltage-voltage curve, which can be acquired during commissioning and then updated as the battery pack ages or wears out due to use/non-use.

The systems, controllers, and methods provided in the present disclosure provide a number of advantages. For example, various battery packs having different qualities, such as used EV battery packs, may be used. There is no need to pre-select or remove the battery pack. The system, controller and method extend the life of some or all of the battery packs, and they also provide flexibility in maintaining and upgrading the system.

Example

For illustration only, an example energy storage system having four battery packs is used. The four battery packs are connected in parallel, and each of them is connected with a single converter. Fig. 5-9 show data from a comparative example, while fig. 10-14 show data from an experimental example following the method of the first embodiment described above.

The battery pack is maximally discharged at 0.5C and charged at 0.5C. A C rating of 0.5C represents the battery usable capacity of a battery pack used (charged or discharged) within two hours. These capacity and voltage characteristics are different, so their recommended/allowed maximum charge and discharge rates are different. Assume that the maximum total rated power of the battery packs 1, 2, 3 and 4 is 3.16kW, 6.66kW, 6.95kW, 7.71kW, respectively. The maximum total power is based on the C rating. For example, if the C rating is 0.5C according to the specification, a 10kWh battery has a maximum power of 5 kW. The actual power charged or discharged from the battery pack is different from its maximum power and is determined according to the methods described herein.

It is also assumed that the voltage distribution parameters (V) for each battery are also in the same order from lowest to highest as the maximum power for each battery when the battery is at 100% soc. In fig. 10-14, the order of V of the battery packs is an increasing order from battery pack 1, battery pack 2, battery pack 3 to battery pack 4 (with highest V). The capacities (Dimax) of battery 1, battery 2, battery 3 to battery 4 were 6.32, 13.32, 13.90, and 15.42kWh, respectively.

An exemplary profile of the total power demand or schedule (D) required from the exemplary system at different time intervals (each having 15 minutes) is shown in table 1 and in fig. 5. Each battery pack is equally ranked, and thus equally discharged or charged.

Table 1: total power demand of the system (D) for 40 15 minute time intervals

As shown in table 1, the total power demand (D) is negative for discharge, positive for charge, and is divided among the four battery packs by the controller 60. In the comparative example, the total power demand is equally divided among the four battery packs.

Tables 2 and fig. 6-9 show the respective discharge powers from each battery pack (battery packs 1, 2, 3 and 4, respectively) to meet the total power requirements as shown in tables 1 and fig. 5.

Table 2: corresponding discharge or charge power of each battery pack in comparative example

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As shown in table 2 and fig. 6-9, the four battery packs are typically individually scheduled with equal power. In the event that one or more battery packs have reached their 0 or 100% SOC, they rebalance to adjust the power between each other. At each instant, the power scheduled from all of the battery packs is equal, except that some battery packs have reached a zero power state. For example, in each of the 12 th and 32 th time intervals, two battery packs have SOCs or capacities reaching zero.

Fig. 10 shows the total power demand or schedule required by an exemplary system comprising four battery packs (battery packs 1, 2, 3 and 4) at different time intervals (each having 15 minutes) for the experimental example. The battery packs are ranked in order of increasing voltage distribution parameter (V) as a discharge order, with the battery pack having the lowest V being discharged first. The data in fig. 10 are the same as those in fig. 5 and table 1.

As described above, it is also assumed that when the battery packs are at 100% soc, the voltage of each battery pack is also in the same order from lowest to highest V as the maximum power of each battery pack from lowest to highest. For simplicity, it is also assumed that the voltage order from lowest to highest remains the same after every 15 minute increment when a new ranking order is established.

Tables 3 and fig. 11-14 show the respective discharge power from each battery pack (battery packs 1, 2, 3 and 4, respectively) to meet the total power demand as shown in fig. 10.

Table 3: respective discharge or charge power of each battery pack in experimental example

As shown in table 3 and fig. 11-14, the battery packs are scheduled with different powers, respectively. In the event that one or more battery packs have reached their 0 or 100% SOC, they rebalance to adjust power between the battery packs.

The differences between fig. 6-9 and fig. 11-14 are most evident when comparing fig. 9 and fig. 14. The battery pack 4 is the strongest battery pack. As shown in fig. 5, the battery pack 4 is significantly used for equal ranking. However, as shown in fig. 14, the battery pack 4 is used less frequently. Thus extending its lifetime. Weak batteries are used more frequently and will be replaced when they are not operational. The two sets of graphs and tables show that the power curves of the battery packs differ significantly between the experimental examples and the comparative examples. This ranking order results in more frequent use of "lower quality" battery packs, so they will be replaced. This will result in a more uniform spectrum of the battery as the energy storage system ages.

The methods and systems described herein may be embodied, at least in part, in the form of computer-implemented processes and apparatuses for practicing those processes. The disclosed methods may also be embodied at least in part in the form of a tangible, non-transitory machine-readable storage medium encoded with computer program code. The media may comprise, for example, RAM, ROM, CD-ROM, DVD-ROM, BD-ROM, hard disk drive, flash memory, or any other non-transitory machine-readable storage medium, or any combination of these media, wherein, when the computer program code is loaded into and executed by a computer, the computer becomes an apparatus for practicing the method. The method may also be embodied at least in part in the form of a computer into which computer program code is loaded and/or executed such that the computer becomes an apparatus for practicing the method. When implemented on a general-purpose processor, the computer program code segments configure the processor to create specific logic circuits. The method may optionally be implemented at least partly in a digital signal processor formed by an application specific integrated circuit for performing the method. The computer or control unit may operate remotely using a cloud-based system.

Although the present subject matter has been described in terms of exemplary embodiments, the present subject matter is not limited thereto. Rather, the appended claims should be construed broadly to include other variants and embodiments which may be made by those skilled in the art.

Claims

1. A system, comprising:

a plurality of battery packs;

one or more power converters, each coupled with at least one of the plurality of battery packs and configured to convert Direct Current (DC) from one battery pack to Alternating Current (AC) or vice versa; and

a controller coupled to the plurality of battery packs and the one or more power converters, the controller comprising one or more processors and at least one tangible, non-transitory machine-readable medium encoded with one or more programs configured to perform the steps of:

receiving a total power demand (D) that needs to be scheduled from or charged to the system;

characteristic data of each battery pack including a maximum voltage (V _imax ) Minimum discharge voltage (V) _imin ) And at presentVoltage (V) _i )；

Based on V _imax 、V _imin And V _i Determining a voltage distribution parameter (V _i *)；

Based on the voltage distribution parameter (V _i * ) Ranking the plurality of battery packs by assigning a ranking to each battery pack as a sequence of discharging or charging;

determining a respective discharge or charge power for each battery pack based on the ranking and the total power demand (D) for each battery pack; and

providing signals with instructions to the plurality of battery packs and the one or more power converters to discharge from or charge to the plurality of battery packs and/or to keep a particular battery pack idle based on the respective discharge or charge power of each battery pack.

2. The system of claim 1, wherein the plurality of battery packs are heterogeneous battery packs selected from a new battery, a secondary Electric Vehicle (EV) battery, or a combination thereof.

3. The system of claim 1, further comprising one or more Battery Power Management Units (BPMUs), each BPMU connected to one or more battery packs and configured to monitor the one or more battery packs and provide characteristic data of the one or more battery packs to the controller.

4. The system of claim 1, wherein the controller is configured to determine the voltage distribution parameter (V _i * ) Ranking the plurality of battery packs in ascending, descending, or random order, and the power is respectively determined in the voltage distribution parameter (V _i * ) Is discharged or charged in the ascending, descending or random order.

5. The system of claim 1, wherein the controller is configured to operate byTo determine the respective discharge or charge power of each battery: based on the respective maximum total rated power (d _imax ) The respective discharging or charging powers are assigned in the order for discharging or charging until the total power demand (D) is reached.

6. The system of claim 1, wherein the system is an electrical energy storage system and the total power demand is provided from an upper energy management system.

7. The system of claim 1, wherein the controller is configured to provide the signal with instructions for a predetermined time interval and to re-determine the respective discharge or charge power of each battery pack by repeating steps after the end of the time interval or when a voltage collapse of the battery pack occurs.

8. A controller for controlling discharge or charge of a system comprising a plurality of battery packs, comprising one or more processors and at least one tangible, non-transitory machine readable medium encoded with one or more programs configured to perform the steps of:

characteristic data of each battery pack including a maximum voltage (V _imax ) Minimum discharge voltage (V) _imin ) And the current voltage (V _i )；

9. The controller according to claim 8, wherein the controller is configured to control the voltage distribution parameter (V _i * ) Ranking the plurality of battery packs in ascending, descending, or random order, and the power is respectively determined in the voltage distribution parameter (V _i * ) Is discharged or charged in the ascending, descending or random order.

10. The controller of claim 8, wherein the controller is configured to provide the signal with instructions for a predetermined time interval and to re-determine the respective discharge or charge power of each battery pack by repeating steps after the end of the time interval or when a voltage collapse of the battery pack occurs.

11. The controller of claim 8, wherein the controller is configured to discharge power from the plurality of battery packs to a grid or load or to charge power from the grid or load to the plurality of battery packs.

12. A method for controlling discharge or charge of a system comprising a plurality of battery packs, the control being by a controller in the system, comprising:

13. The method of claim 12, wherein the plurality of battery packs are heterogeneous battery packs selected from a new battery, a secondary use Electric Vehicle (EV) battery, or a combination thereof.

14. The method of claim 12, wherein

Determining the voltage distribution parameter (V) of each battery pack using equation (1) _i *)：

V _i *＝(V _i -V _imin )/(V _imax -V _imin ) (1)。

15. The method according to claim 12, wherein the plurality of battery packs are arranged according to the voltage distribution parameter (V _i * ) Ranking in ascending order of (a).

16. The method according to claim 12, wherein the plurality of battery packs are arranged according to the voltage distribution parameter (V _i * ) Ranking in descending order of (a).

17. The method of claim 12, wherein the plurality of battery packs is in accordance with the per battery packVoltage distribution parameter (V) _i * ) Ranking in a random order.

18. The method of claim 12, wherein the respective discharge or charge power of each battery is determined by: based on the respective maximum total rated power (d _imax ) The respective discharging or charging powers are assigned in the order for discharging or charging until the total power demand (D) is reached.

19. The method of claim 18, wherein a particular battery pack remains idle when the respective discharge or charge power is assigned to zero.

20. The method of claim 12, further comprising: some or all of the steps are repeated to re-determine the respective discharge or charge power of each battery pack after the end of a predetermined time interval or when a voltage collapse of the battery pack occurs.